Ferrite core for electrodeless flourescent lamp operating at 50-500 khz

Abstract

An electrodeless fluorescent lamp operating at relatively low frequencies (50-500 kHz) whereby a ferrite core is utilized to generate the necessary magnetic and electric fields to maintain the discharge where the core material is Mn—Zn type combination due to its low power losses, 400 mW/cm 3 , in the frequency range of 50-100 kHz and magnetic field strengths of 150 mT. Furthermore, the material may cover a variety of atomic percentages of Mn and Zn added to Fe 2 O 3 base to obtain favorable grain boundary and crystalline structure, resulting in a practical ferrite core material, having a Curie temperature greater than 200° C. Such material enables the operation of electrodeless fluorescent lamps with powers ranging from 10 W to about 250 W at low frequencies, as mentioned above, in such a manner that ferrite core losses constitute less than 20% of the lamp power and heat generated by core losses is minimized.

As our invention we claim:  
     
         1 . An electrodeless flourescent lamp comprising: a glass envelope containing a fill of mercury and an inert gas; 
 a ferrite core disposed adjacent to said envelope, said core comprising a mixture of iron, manganese and zinc, the weight ratio of the manganese and zinc to the iron being between about 0.2 and 0.7, the weight ratio of the zinc to the manganese being between about 0.2 to 2.0.    
     
     
         2 . The electrodeless lamp according to  claim 1  wherein said lamp operates at relatively low frequencies of 50-500 kHz, said ferrite core to generating a magnetic field whereby to form a practical lamp which operates with power efficiency not lower than 80%.  
     
     
         3 . The electrodeless lamp according to  claim 1  wherein said core is of a Mn—Zn ferrite type where the atomic percentage of Mn and Zn can vary over a wide range resulting in very low power losses when current is applied to a coil in close proximity to the core material thereby providing high lamp power efficiency.  
     
     
         4 . The electrodeless lamp according to  claim 1  wherein said core is in the form of a hollow cylinder and when operated at 100 kHz has less than 100 mW/cm 3  losses at 80 mT magnetic field and less than 400 mW/cm 3  at high magnetic fields at 150 mT.  
     
     
         5 . The electrodeless lamp according to  claim 1  wherein said core material enabling the operation of electrodeless fluorescent lamps at 50-500 kHz, with power efficiency and lamp efficacy comparable to those in lamps operated at 2.65 MHz thereby resulting in a lower overall system cost.